1. Field of the Invention
This invention relates to fully and partially automated vehicular mechanical transmission systems of the type utilizing controlled engine fueling to cause synchronous conditions for engaging positive clutch members associated with a target gear ratio. In particular, the present invention relates to a control system/method for an at least partially automated mechanical transmission system wherein the requested engine speed during a gear engagement operation is set at a value alternately above and then below, or vice versa, true synchronous engine speed (i.e., ES=IS=OS*GR.sub.T) by a preselected amount (the "dither") to assure full penetration of the engaging positive clutch and to minimize synchronous overshoot.
2. Description of the Prior Art
Fully and partially automated mechanical transmission systems intended for vehicular use are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,648,290; 4,595,986; 4,850,236; 5,053,959; 5,109,721; 5,261,288; 5,315,218 and 5,335,566, the disclosures of which are incorporated herein by reference. In these types of systems, engine fueling/braking control is typically utilized to achieve synchronous conditions for engaging a target gear ratio.
The prior art automated transmission systems typically utilized electric, electro-mechanical, electro-hydraulic or electro-pneumatic type actuators to operate a plurality of generally parallel shift rails or a single shift shaft mechanism, or the like, through an X-Y mechanism and/or a plurality of linear actuators. Axially movable jaw clutch members are selectively axially positioned by shift yokes (also called shift forks) carried by shift shafts or block mechanisms, which are axially positioned by shift fingers, pistons and the like. Shift mechanisms of this type may be seen by reference to U.S. Pat. Nos. 4,445,393; 4,873,881; 4,899,607; 4,920,815; RE 34,260; 4,945,484; 5,000,060; 5,052,535; 4,964,313 and 5,368,145, the disclosures of which are incorporated herein by reference.
The prior art control methods/systems were not totally satisfactory, especially for relatively non-compliant electric motor-operated shifters, as during the synchronization and jaw clutch engagement phase of a shift into a target gear ratio, the engaging positive jaw clutch members could become torque locked in an only partially engaged condition. If this condition is allowed to exist for a prolonged period of time, excessive wear and/or damage to the jaw clutch and/or the shift actuator mechanism may result.